Midea MM720CRO-PM0C, Service Manual

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Ⅲ
.REPAIRING METHOD OF SEVERAL BREAKDOWN
1. Repair when there occurred large amounts microwave leakage. There are many factors, which may cause microwave leaking.
Following mentioned may be the main cause of microwave leakage:
(1) The door deformed, the hinge loosed or damaged that caused the door can not close tightly.
(2) The door pressing cover or the embed piece damaged or come off.
(3) Obvious damage or uneven of the oven.
(4) There are filth between the door and the oven.
(5) The door and the oven are serious loosed after the door closed.
(6) The crack of the door shielding net cover.
Before repairing, check whether the above listed point are existed, if not, you can start the microwave oven. Place a
graduate of about 275ml water at the middle of the glass tray, close the door, time set at 3 minutes, power at high,
makes the oven operating in normal. Rectify the microwave leakage measure, measure the amount of the microwave
leakage around the oven with its probe. If there are places which the leakage exceed the standard requirement, then
repair them accordingly. If the leakage amount exceed 1.0 mW/cm
2
at the left door crack, then pull out the power plug,
take down the outer case, adjust the screws of the hinge to less the gap between the door and the oven. Then measure
again, the leakage amount should less than 1.0 mW/cm
2
. Generally, it should be controlled below 0.8 mill watt/cm
2
with
some allowance.
If the leakage occurred at the right door crack, adjust the screws that fix the interlock holder and the hook. If the leakage
is on the larger side at the right-above of the oven, then adjust the upper screw. Loosen out the screw, push the door
close to the oven to hook the door hook with the plastic parts, then tighten the screw again. If the leakage is larger at
the right-below, then adjust the lower screw. Loosen the screw, push the door close to the oven to hook the door hook
with the switch holder tightly, then tighten the screw again, and open and close the door repeatedly to check whether the
door can operate flexibly, whether the hook and the switch are in their normal position. If it is not in position, then adjust
the door hook and the switch holder the loose between the door and the oven, then measure the leakage with
microwave leakage measure again.
If there still exist microwave leakage, measure near the magnetron with the probe of the microwave leakage measure. If
the leakage is larger, the oven should be turned off and check whether the 2 or 4 screws which fix the magnetron have
been loosed, if loosed, twist them tightly with socket wrench. If the screws are fixedly, then the magnetron should be
take down to check the copper filament weaved washer of the magnetron has been placed well or whether the wave
guide housing coupling has been oxidized or have lacquer on it. If do have, scrape the oxidized layer or the lacquer off,
when fix the magnetron, the copper filament weaved washer must be placed well, the screws must be twist tightly. Then
turn on the oven and measure again until it complies with the requirement. If the microwave leakage is larger at those
hole position of the window board, the oven should be turned off to inspect whether there are crack among them. If
several holes formed a crack, it would enlarge the microwave leakage. If that is the case, it indicates the door has
broken, and should be replaced with a new door.
5-6
FIG.5-9
FIG5.10